Just reviewing a lease and the rider requires me to pay up to $100 in repairs per repair occurrence. This is surprising to me. Is it something that landlord can ask? Is it common?

There are several provisions in the lease that are contrary to NYC rent regulations (repping I have no child under ten, giving me 30 days to make a lead paint complaint, putting me in charge of hiring my own exterminator). For the most part I'm just letting those slide, since no point arguing unless a problem arises in which case I should be protected.

But this $100 per repair thing concerns me. Is that a responsibility the landlord can place on me?

It is absolutely illegal for a landlord to discriminate against potential renters because they have children, regardless of age.* That's not just an NYC thing, it's part of the federal Fair Housing Act.

Discrimination in Housing Based Upon Familial StatusThe Fair Housing Act, with some exceptions, prohibits discrimination in housing against families with children under 18. In addition to prohibiting an outright denial of housing to families with children, the Act also prevents housing providers from imposing any special requirements or conditions on tenants with custody of children. For example, landlords may not locate families with children in any single portion of a complex, place an unreasonable restriction on the total number of persons who may reside in a dwelling, or limit their access to recreational services provided to other tenants. In most instances, the amended Fair Housing Act prohibits a housing provider from refusing to rent or sell to families with children. However, some facilities may be designated as Housing for Older Persons (55 years of age). This type of housing, which meets the standards set forth in the Housing for Older Persons Act of 1995, may operate as "senior" housing. The Department of Housing and Urban Development (HUD) has published regulations and additional guidance detailing these statutory requirements.